Tennessee's roadways are in good overall condition, showing marked improvement over the last two decades, according to a report released by the Reason Foundation, a public policy think tank.

State highways, Interstates and rural roads also appear better-than-average in Greene County, a Tennessee Department of Transportation (TDOT) spokesman said Friday.

The policy organization's report is good news for the Volunteer state, several TDOT officials said. The roadway assessment, released in late February, examined 20 years of highway data from 1989 through 2008.

The study, "Are Highways Crumbling? State Performance Summaries," took information from all 50 states, assessing seven key categories that dealt mostly with the condition of major highways and Interstates, as well as rural roads and bridges.

Tennessee improved in all seven categories -- one of only 11 states in the U.S. to do so.

"This report is a testament to the focus TDOT has placed on maintaining our infrastructure, aggressively repairing and replacing aging bridges, increasing safety and managing congestion," TDOT Commissioner John Schroer said in a news release.

"This is truly exceptional when you consider we are one of only five DOT's in the nation with no transportation debt," Schroer added.

Locally, main roads seem to be in solid condition, TDOT spokesman Mark Nagi said.

According to Nagi, a good way to judge an area's road conditions is through use of the Pavement Quality Index (PQI).

Using the PQI, Nagi explained that a rating scale from 0-5 is used to assess the quality of a region's roadways.

A zero is given for the worst pavement conditions, and a 5 is assigned for the best. A 3.25 PQI score is considered good, Nagi said.

"The state routes in Greene County average PQI is 3.41 while the Region 1 (much of East Tennessee) average is 3.49 and the statewide average is 3.85," Nagi said, based on 2010 data.

The 2012 PQI reports were are not yet available, he said.

"One issue that the counties in Region 1 experience more in relation to the rest of the state is that we have more winter weather than the rest of the state typically, which creates a greater stress on the pavements due to de-icing treatments and freeze/thaw cycles," Nagi said.

Greene County's Interstate sections have an average PQI of 4.10, Nagi added.

"The Greene County Highway Department does a lot of their bridge repairs and replacements with their own people," he pointed out. "The county has improved a lot of county bridges over the years."

Greene County Road Superintend David Weems had not yet reviewed the study's results on Friday morning, but was pleased with what he knew so far.

"We strive to try to keep our main roads in good condition," Weems said.

"With approximately 1,200 miles of roads, it's a process. I do think in general ... our roads are in better condition than some of the counties I've visited."